Microstructure and properties at bonds of diamond grains and Ni[sbnd]Cr filler alloy by fiber laser brazing

Abstract

Advanced laser technology has been used in laser brazing to bond diamond grains in metal matrix to achieve some distinctive advantages such as high protrusion heights and large gaps of diamond grains. However, laser brazing has not been widely adopted as expected to produce various diamond tools since that bonding mechanisms, microstructures and characteristics of bonded interfaces have not fully investigated. In this paper, the experimental study was performed for using fiber laser brazing to bond diamond grains on steel substrate with NiCr filler alloy. Microstructures, graphitization, and shear force at the bonded interface were especially analyzed. The experiments led to the following outcomes: (1) the interface of diamond grains and NiCr alloy was a wavy surface with an average thickness of 7 μm. (2) Two types of carbide, i.e., Cr3C2 and Cr7C3, were generated on the brazed surface; Cr3C2 was lath-shaped and generated at first, and Cr7C3 was prismatic and built upon Cr3C2. (3) The interface of diamond grains and NiCr alloy was rough and accompanied by graphitization. (4) The shearing test showed that an average force of 138 N was applied to debone single diamond grain from filler metal.